Changes in a single variable can be shown accurately by one-dimensional elements such as by position along an axis or by lines. Using area or volume at best confuses the reader since it is not ...

Both variables move together in the same direction when they change. Decreases in one variable resulting in the opposite change in the other variable are referred to as negative covariance.

How to Make a Chart on Excel With More Than One Variable. One of the more useful features in Microsoft Excel is Insert Charts. You can create a wide variety of charts: bar, line, pie and others.